Preformed pontic patterns



July 29, 1969 H. SUSMAN ETAL PREFORMED PONTIC PATTERNS Filed July 18, 1966 FIG. 4

INVENTORSI F I 6- 2 HARRY SUSMAN JON E. SUSMAN ATTORNEYS United States Patent 3,457,644 PREFORMED PONTIC PATTERNS Harry Susman and Jon Edward Susman, both of 6439 Prestoushire, Dallas, Tex. 75225 Filed July 18, 1966, Ser. No. 566,157 Int. Cl. A61c 13/08 U.S. Cl. 32-2 3 Claims ABSTRACT OF THE DISCLOSURE A preformed posterior pontic pattern made of a solid, non-deformable, plastic material which is shaped in the form of a thin shell formed by two sidewalls, a rear portion, and a wall having an occlusal surface, the base of the sidewalls being shaped to correspond to a gum ridge and cooperate with a hardenable plastic layer over a gum ridge, which layer, after hardening in contact with the base of the sidewalls, will form an an integral bottom portion of the pontic pattern.

The present invention relates to preformed pontic patterns, and in addition, it further relates to the method of making pontics.

Pontics, i.e., artificial teeth which replace missing teeth, are so widely employed in the art of dentistry as to require no description as to their purpose and general structure. Various methods have been used to make pontics in the past.

Probably the most widespread prior art method of making back or posterior pontics has utilized wax. The process is cumbersome at best, and it has proved quite diflicult to make a high quality pontic of proper shape that truly fits the mouth.

A sheetlike plastic member with a single extending ridge has been utilized in combination with wax and a labial pontic portion for making an anterior pontic. This is not only a tedious process, but the end product is often lacking in integrity of shape, has a poor appearance, and does not fit the mouth of the patient properly. Moreover, the gold casting which ultimately takes the place of the wax and the plastic backing has a tendency to fracture or break along its connection with the labial pontic portion, or the labial pontic portion often breaks at the points of high stress where it engages the interconnecting ridge member of the gold backing.

An object of the present invention is to materially simplify the making of high quality pontics to replace both back and front missing teeth. A further object is to provide preformed pontic patterns which make it possible to simply form such high quality pontics. Yet a further object is to provide a preformed pontic pattern which makes possible a saving of time and gold, While still providing a better fit for the pontic formed therefrom. Moreover, it is an object to provide a preformed pontic pattern which will result in a more sanitary condition for the patient as a result of the pontic ultimately formed from the pattern. Still a further object is to provide a pontic pattern which may be tried in the patients mouth, prior to casting of a pontic unit, to verify the integrity of the fit.

In accordance with the present invention, a preformed pontic pattern is provided. The pontic pattern is of a type material which oxidizes under oxidation conditions to leave substantially no residue. Preferably the material of construction is plastic. Typically the preformed pontic pattern has certain outer surface regions which define at least a part of the outer periphery of a pontic based on the pattern.

In one embodiment, the pontic pattern is roughly boxshaped to correspond to the shape of a posterior tooth. Such box-shaped pattern is open at the buccal and prefer- "ice ably, but not necessarily, open at the base. In another embodiment, the pontic pattern is shaped to generally correspond to the lingual portion of an anterior tooth. It has labial pontic portion engaging means on its labial face. Its engaging means preferably comprises a widened post member extending forward from the front face of the pontic pattern. The post member terminates in an enlarged flange portion which extends outwardly from either side of the post in the vicinity of the base of the pontic pattern. Preferably the post is undercut somewhat so that it engages a mating part in a manner that prevents motion or movement between the two in all directions except axially of the post.

Considered in its process aspects, the present invention contemplates placing a viscous formable material over the ridge of an articulated model of a patients mouth at the location where a missing tooth is to be replaced with a pontic. A pontic pattern, after being ground to roughly fit the ridge, is placed in position with its base portion overlying the viscous formable material in the location where the missing tooth is to be replaced. The viscous material is solidified so that fusion occurs between the applied material and the preformed pontic. When the preformed pontic is removed from the articulated model, the added hardened material adheres to it and becomes an integral part thereof. The resulting pontic pattern has a high integrity of shape conforming rather precisely to the ridge of the articulated model. If desired, viscous formable material may be added to the preformed pontic pattern portion to build up its sides or otherwise change its shape to better fit in its intended position with adjacent teeth. Moreover, viscous formable material may be used to join the pontic pattern to adjacent crown patterns to provide an integral pattern unit which may be placed in the patients mouth to check fit before a pontic unit is cast using the integral pattern.

For a more complete understanding of the present invention and for further objects and advantages thereof, reference may now be had to the following description taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a perspective view of an embodiment of a preformed pontic pattern which is used in making a posterior pontic;

FIGURE Za-Ze are side sectional views which illustrate how the pontic pattern of FIGURE 1 may be used to manufacture a high quality pontic;

FIGURE 3 is a schematic facial (buccal) View showing a pontic pattern joined to adjacent crown patterns for the purpose of providing a pontic pattern unit which may be fit directly into a patients mouth.

FIGURE 4 is a side view illustrating an embodiment of a pontic pattern of the type used in making an anterior pontic;

FIGURE 5 is a rear view of the labial pontic portion which mates with the product of the pattern of FIGURE 4;

FIGURE 6 is a side view of an anterior pontic which has been manufactured from the plastic pontic pattern of the type illustrated in FIGURE 4 and which includes the labial porcelain or plastic pontic portion illustrated in FIGURE 5 as a part thereof; and

FIGURE 7 is a cross section taken through 77 of FIGURE 6.

Referring now to the drawings in greater detail, in FIG- URE 1 preformed pontic pattern 11 is made of a plastic material which can be oxidized to leave substantiailly no residue. This is important since ultimately a gold casting will be made by the investment casting method utilizing the pontic pattern.

The pontic pattern 11 is shaped generally as a back tooth. Consequently, it is roughly speaking box-shaped.

The wall or shell thickness of such pontic pattern is preferably minimized in order to conserve the amount of gold required to accomplish the ultimate casting made from the pattern. Preferably, but not necessarily, the pontic pattern 11 is open at its base or ridge portion.

In using the pontic pattern 11, the pattern is first placed on an articulated model in a location where it is to replace a missing tooth. It is oriented with its open front or buccal portion facing buccally. It has wall 12 which provides an occlusal surface, a lingual Wall 13, and sides 14 and 15. As shown in FIGURE 2a, the pontic pattern 11 is positioned adjacent the gum ridge 21 (as seen from the side in section) and an observation is made by the dentist to determine whether the arch of the pattern roughly conforms to the gum ridge. If it does not, plastic is groundoff or otherwise removed to steepen the arch region of the pontic pattern to bring it into closer conformity with the ridge. The pontic 11 is illustrated in FIGURE 2b after the arch has been shaped, as discussed.

A viscous formable material such as methyl methacrylate plastic is painted over the ridge. This forms the plastic layer 23 on the ridge 21. It is desirable that a release agent, such as petrolatum or liquid foil or the light be lightly apaplied over the ridge 21 on the articulated model before applying the viscous material to facilitate a later release.

The pontic pattern 11 is firmly implaced on the ridge 21 to overlie the layer 23 after that layer has cured somewhat. This is illustrated in FIGURE 2c. The pontic pattern 11 and the plastic layer 23 are allowed to remain in such contact until the layer 23 fuses to the pontic pattern 11 and becomes an integral part thereof. At that time the plastic layer 23 has substantially cured to form a solid or hardened plastic material.

After fusion and hardening is completed, the pontic pattern is removed from the articulated model, the removal preferably being facilitated by a thin film or release agent, such as liquid foil or petrolatum as previously referred to herein. If necessary, a small amount of grinding removes any portions of the bonded layer which are not desired, such as regions of the applied viscous material which flowed further down On the gum ridge than necessary. The finished pontic pattern, after processing on the articulated model, as described above, is illustrated in FIGURE 2d.

The processed preformed plastic pontic of FIGURE 2d is thereafter used in an investment casting process by which an investment mold is made. The plastic material is burned-out i.e., oxidized, by heating under oxidizing conditions. Finally gold is introduced into the investment mold to cast the pontic shell, which has the same configuration as the investment mold.

The gold pontic shell is implaced on the articulated model and joined to adjacent crowns by processes Wellknown in the art of dentistry. The gold pontic shell is filled with a porcelain or plastic material that closely resembles the color of the patients teeth. Various tinting or coloring processes may be used for the filler material as desired. The filled gold shell, which constitutes the final pontic product, is illustrated in FIGURE 2e, wherein the plastic or porcelain filler is indicated by the numeral 25 and the gold pontic shell is identified by the numeral 27.

In some instances, the pontic pattern 11 will not have sufiicient width to properly mate with adjacent teeth to form a high quality pontic. This can be remedied by painting on or otherwise applying a quantity of viscous formable material on the sides 14 and 15 of the pontic pattern while it is in position on an articulated model 'of the patients tooth structure.

Sometimes it is desirable to make a fitting in the pa tients month during the course of processing a pontic in accordance with the present invention. This may be accomplished by actually fitting a preformed pontic pattern into a ptaients mouth after the pontic pattern has been joined to adjacent crown patterns. This technique is illustrated in FIGURE 3, wherein plastic crown patterns 31 and 33 are disposed on an articulated model to overlie the model crown preparations 31 and 33, respectively. Plastic crown patterns 31 and 33 may be made of various plastic materials, e.g., of polymethylmethacrylate. The crown patterns 31 and 33 are joined to a preformed pontic pattern, such as the pattern 11 previously discussed in connection with FIGURES 1 and 2, by means of a viscous formable material, e.g., polymethylmethacrylate carried by methylmethacrylate monomer. Thus viscous liquid plastic forming material is applied to form joint 35, which joins side 14 of preformed pontic pattern 11 to the adjacent side of crown pattern 31 and to form joint 37, which joins the side 15 of preformed pontic pattern 11 to the adjacent side of crown pattern 33. After the applied viscous material cures, the crown patterns 31 and 33 and the preformed pontic pattern 11 of FIGURE 3 to form a single unit which may then be tried in the patients mouth to verify the integrity of the fit. Thereafter the joined crown-pontic pattern unit is utilized as an integral pattern in an investment casting process. The product is a gold casting which conforms to shape of the integral pattern. Porcelain or plastic material as filler may then be applied in analogous fashion to that illustrated and discussed in conjunction with FIGURE 2e in order to complete the the end product, which is a unitary dental prosthesis.

A somewhat different embodiment of the present invention is preferred for front or anterior teeth, where appearance is at a premium. In this case, it is preferred that a preformed labial porcelain or plastic tooth pontic portion be used and that it be connected to a lingual portion of the pontic so that no gold whatsoever is visible.

In making such a pontic, the lingual preformed pontic pattern 41 of FIGURE 4 is most useful. This pattern is preferably of plastic and shaped generally as the rear or lingual half of an anterior tooth. Its front or labial face 42 has a widened post portion 43 extending forwardly therefrom. The post portion 43 is undercut on both sides, as is indicated at 44 and 45 (FIGURES 4 and 7). Flange portions 47 extend from either side of post portion 43- at its base end and connect with the labial face 42 of lingual pattern 41. Such flanges provide a region for seating, and also strengthen the post portion 43 somewhat.

The pontic pattern 41 is implaced on an articulated model and processed generally in accordance with the steps illustrated in FIGURES 2a-2d, as previously explained herein. A gold pontic portion is then made by the investment casting process to conform to the shape of the plastic pontic portion 41. This product is identified in FIGURE 6 by the numeral 41'. To it a porcelain or plastic labial pontic portion 51 is attached. As is best seen in FIGURE 5, labial pontic portion 51 has on its lingual or rear face a recessed region 53 shaped to mate precisely with the post member 43 and flange members 47, the undercut portions 44 and 45 of post 43 being engageable with grooves 44' and 45' (note dotted lines in FIGURE 5) and flange portions 47 being engageable with flange seats 47' on labial pontic portion 51.

The pontic of FIGURE 6 is a high quality product which is then implaced in the mouth of the patient by conventional processes which are known in the art of dentistry.

Various plastic materials may be used for the preformed pontic pattern of the present invention, the preferred material being polymethyl methacrylate. Moreover, the viscous formable material used in conjunction with the pontic pattern to precisely fit the ridge and, if desired, to Widen or otherwise alter the pattern or join it to adjacent patterns to form a unitary structure, may likewise be selected from a wide variety of plastic materials, the preferred material formed by the hardened viscous formable material again being polymethyl methacrylate or a copolymer of the same. Exemplary of specific mateterials satisfactory for forming a preformed pontic pattern in accordance with the present invention, as well as for serving as the viscous formable material utilized in the practice of the present invention are the following:

(a) Duralay powder 1057N and liquid 1151N, marketed through Reliance Dental Manufacturing Company, Chicago, 111.

(b) Replica Plastic Filling Material (a powder) and Replica Liquid, marketed through Cosmos Dental Products, Inc., 219 E. 44th Street, New York 17, NY. (preferably used in a ratio of 3.522, of powder to liquid in order to make the viscous formable material).

(0) Myersons Self-Curing Crown and Bridge Resin, crosslinked copolymer, and Myersons cross-linked monomer for Myersons Crown and Bridge Resin, marketed by Myersons Tooth Corporation, Cambridge, Mass.

(d) Rimseal powder and Rimseal liquid, marketed by Harry J. Bosworth Co., Chicago, Ill.

To generalize regarding the preferred available commercial preparations, they usually are powdered acrylic resins, e.g., polymethyl methacrylate, used in conjunction with an acrylic monomer, e.g., methyl methacrylate monomer, to form a liquid material which is self-curing at room temperature. During the curing process, the liquid becomes increasingly viscous, until finally solid acrylic plastic results. While the precise compositions of the various commercially available materials are not known, the various powders available are often polymethyl methacrylate and contain a small quantity of catalyst such as benzoyl peroxide or diisobutylzonitrile. The liquid material used therewith is principally methyl methacrylate monomer, and generally contains an inhibitor, such as hydroquinone, and a chemical accelerator, such as an organic tertiary amine, e.g., dimethyl-para-toluidine, or a sulfinic acid.

Some preferred materials commercially available include a copolymer of methyl methacrylate and another monomer. For example, the copolymer may be ethyl or butyl methacrylate, together with methyl methacrylate.

While polymethyl methacrylates and related plastics are preferred, any material may be utilized as a material of construction for the preformed pontic pattern of the present invention provided that it forms a solid having structural integrity at room and body temperatures such that the material will not distort or lose shape upon being manipulated by a dentist or technician, provided that it burns-out during the course of the casting process, and provided that it is capable of achieving a smooth surface. Moreover, any material may be utilized for the viscous formable material employed provided that it has the qualities referred to in the foregoing sentence, and in addition, that will adhere to the preformed pontic pattern. Also, it is distinctly preferred that the viscous form-i able material be cold curing, or at least curable at a temperature not far above room temperature.

What is claimed is:

1. A preformed pontic pattern made of a solid plastic material which has structural integrity at room and body temperatures, will not distort upon handling, and will oxidize under oxidizing conditions to leave substantially no residue, said pontic pattern being generally shaped to correspond to a posterior tooth and comprising a thin shell formed by two sides, a rear portion, and a wall having an occlusal surface, the base of the sidewalls of said pattern being generally shaped to fit a gum ridge, and being thereby adapted to cooperate with a soft but hardenable plastic layer on said gum ridge which conforms to the shape of said gum ridge, and which layer, after hardening in contact with said base, will form an integral bottom portion of said pontic pattern.

2. The pontic pattern of claim 1 wherein said pattern is open at the base and the buccal.

3. The pontic pattern of claim 2 further comprising an arch-shaped layer of plastic adhered to the base of the sidewalls of said pattern to define a base which conforms in exterior surface shape closely to the shape of a gum ridge in order to adapt a pontic made from said pattern to fit said ridge.

References Cited UNITED STATES PATENTS 2,576,206 11/1961 Barth 26419 2,700,184- l/1955 Levine 26419 3,058,216 10/1962 Cohen 32-12 ROBERT PESHOCK, Primary Examiner 

